Study On Fermentation Process Of A New Biology Preservative Natamycin

Natamycin(Pimaricin)is one of the kinds of macrolide antibiotics,which is produced by several of actinomycetes such as Streptomyces chattanovgensis,Streptomyces natalensis and Streptomyces gilvosporeus.Because it is one kind highly effective anti-fungus antibiotic which can special suppresses the yeast and the mildew,and it is low toxic to the mammalian cells which is compared to other antifungal compounds,it is widely used in food industries and medical treatment.However,the yield of natamycin at present is very low,so the application of natamycin is limited severely due to the high cost of production. Therefore,it is of great importance to enhance the research and development of natamycin production process.In this study,the work was how to increase output of natamycin.The major research contents and results are as follows:A RP-HPLC method and an ultraviolet spectrophotometric method for the analysis of natamycin in fermentation broth were developed.The sample was separated at 35℃on a Dikma Technologies C18(5um,250mm×4.6mm)eluted at a flow rate of 1.00ml/min with a mobile phase of methanol-water-performic acid(50:50:0.05,V/V).Natamycin was detected and quantified by the absorbance at 303nm in the RP-HPLC.The sample was separated by methyl alcohol,and natamycin was quantified by the absorbance at 303nm in the ultraviolet spectrophotometric method.The first one was accurate and needed more time. The second one was simple and rapid,but was influenced by somethings at a time. Therefore,in the experiments,the two methods were used in combination to achieve the purpose that detecting natamycin in fermentation rapidly and accurately.The slope culture medium and seed culture medium were studied.The optimum medium of slope culture medium consisted of:glucose 10g/L,peptone 5g/L,yeast extract powder 3g/L,malt extract powder 3g/L and pH 7.0～7.1.The optimum medium of seed culture medium consisted of:glucose 30g/L,yeast extract powder 6g/L,soya peptone 16g/L and pH7.0.The seed age was 44～48h.The inoculums level was 6%.The optimum medium of fermentation broth was studied.The carbon source was glucose,nitrogen source is admixture of soya peptone and yeast extract powder.The optimum medium was demonstrated through orthogonal design test,and it consisted of: glucose 40g/L,soya peptone 20g/L,yeast extract powder 7g/L and pH 8.0.Based on optimum medium of fermentation broth,the optimization of the fermentation condition was studied.The optimal medium for dissolve oxygen and the temperature on the yield of natamycin fermentation were studied.The result was that a 300mL flask containing 70mL medium was cultivated at 29℃and the agitation speed was 200r/min.The influence of precursors and Mg₃(PO₄)₂ on natamycin production was explored.The result showed:adding 0.2%Mg₃(PO₄)₂ at the beginning and 0.2%sodium propionate at 48h can improve natamycin production of flask to 3.22g/L from 1.71g/L, which was 88.3%higher than that of initial conditions.The batch fermentation and fed-batch fermentation in a 10L bioreactor were studied. Natamycin yield of the batch fermentation was 2.91g/L.It made mycelium stronger by intermittence feeding glucose,and natamycin yield was improved to 3.43g/L.The natamycin yield of fed-batch fermentation was 17.9%higher than that of the batch fermentation.